AUTHOR'S PREFACE. 



When, at the request of Prof. H. F. Osborn, who succeeded the late Prof. O. C. Marsh as 

 chief of the division of vertebrate paleontology of the United States Geological Survey, I under- 

 took to complete Professor Marsh's unfinished volume on the Ceratopsia, it was understood 

 that the work would be attended with certain difficulties that probably would not have pre- 

 sented themselves had Professor Marsh lived to complete the volume himself. The vast col- 

 lection brought together at New Haven, though in part belonging to the United States 

 Geological Survey, would doubtless, had he lived, have remained intact, for the most part, 

 at least, until such time as he had completed his studies, thus enabling him to study the collec- 

 tion together as a unit instead of separated and divided between two distinct institutions. 



Considerable inconvenience has been experienced in the preparation of the present volume 

 by reason of the fact that the material upon which it is based is for the most part scattered in 

 the museums of four different institutions, with none of which the present author is connected, 

 thus necessitating considerable loss of time in travel and rendering it quite impossible to bring 

 together for comparison the types of closely related species. By far the most serious difficulty, 

 however, has been experienced from the lack of sufficient preparation of the large collection of 

 skulls and other material made by the present writer iinder the direction of the late Professor 

 Marsh, many of which still remain unopened in the original boxes in which they were packed 

 in the field. To render this entire collection fully accessible for purposes of study is a work 

 which of itself would require the services for several years of a considerable force of skilled 

 preparators and would entail an expenditure of both time and money far in excess of that 

 allotted for the preparation of the present volume, which, notwithstanding its title, should 

 be regarded rather as an introduction to the study of the Ceratopsia than' as a final report on 

 that interesting group of dinosaurs. It is hoped, however, that in the text and figures not a 

 little new light of interest to the specialist will be thrown on the structure of the Ceratopsia 

 as a group and on the relations of the various genera and species, while at the same time it is 

 believed that those pages relating to the history of the discovery of the Ceratopsia, their prob- 

 able habits, the conditions under which they lived, the causes which led to their extermination, 

 the causes and conditions of the preservation of their remains, the geology and physiography 

 of the region in which they are found, and the difficulties experienced in collecting such huge 

 fossils, the skulls alone of some of which, when prepared for shipment, having weighed upward 

 of 3 tons, will be of interest to the layman. 



Unfortunately only 19 of the lithographic plates planned by the original author for the 

 present volume were completed prior to his death, and, since the Survey has discontinued 

 lithography for illustrations of this character, that uniformity and artistic effect which is 

 shown in the plates of Professor Marsh's other monographs are wanting in the present volume. 

 It is believed, however, that this loss has been at least partially offset by the series of text 

 figures, reproduced from pen-and-ink drawings, which illustrate the text and represent many 

 o'f the more abstruse anatomical details with possibly greater fidelity than would have resulted 

 from the use of lithographs, where, as too often happens, detail of character is sacrificed for 

 artistic effect. 



For aid rendered and for privileges of study in the preparation of the present volume I 

 am indebted to the authorities of various museums. From the late Dr. Charles Emerson 

 Beecher I received every possible aid and opportunity in studying the magnificent collection 

 of Ceratopsia belonging to Yale University. To Dr. George P. Merrill and Mr. Frederick A. 



